Combined Gas Law
Examples and Problems only

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Ten Examples

Example #1: 2.00 L of a gas is collected at 25.0 °C and 745.0 mmHg. What is the volume at STP?

Example #2: The pressure of 8.40 L of nitrogen gas in a flexible container is decreased to one-half its original pressure, and its absolute temperature is increased to double the original temperature. What is the new volume?

Example #3: 1.85 L of a gas is collected over water at 98.0 kPa and 22.0 °C. What is the volume of the dry gas at STP?

Example #4: If the volume of an ideal gas is doubled while its temperature is quadrupled, does the pressure (a) reman the same, (b) decrease by a factor of 2, (c) decrease by a factor of 4, (d) increase by a factor of 2, or (e) increase by a factor of 4?

Example #5: The product of the pressure and volume of a gas, divided by the temperature, is a constant. This is represented by the formula:

PV/T = k

(x) If the pressure and volume of a gas both increase, will the temperature increase or decrease? Explain your answer.
(y) If the pressure is doubled and the volume is tripled, by what factor must the temperature increase or decrease? Show your work.
(z) If the pressure of the gas is decreased by removing some of the gas, is it possible to use the above formula to predict the change in volume and temperature? Why or why not?

Example #6: At constant temperature, if the gas amount in the sample is doubled while the pressure is halved, what will happen to the volume of the gas sample?

Example #7: Using the Combined Gas Law, write each of the six symbolic values in terms of the other five symbolic values.

Example #8: 35.4 mL of hydrogen gas is collected over water at 24.0 °C and a total pressure of 745.0 mmHg. What is the volume of the gas at STP?

Example #9: A tire has 25 air particles and a volume of 205 mL with a pressure of 0.950 atm. If 10 air particles are added the tire, the volume is 215 mL. What is the new tire pressure?

Example #10: At constant temp, if the amount of gas in the sample is doubled while the pressure is halved, what will happen to the volume of the gas sample?


Probs 1-15

Problem #1: A gas has a volume of 800.0 mL at −23.0 °C and 300.0 torr. What would the volume of the gas be at 227.0 °C and 600.0 torr of pressure?

Problem #2: 500.0 liters of a gas in a flexible-walled container are prepared at 700.0 mmHg and 200.0 °C. The gas is placed into a tank under high pressure. When the tank cools to 20.0 °C, the pressure of the gas is 30.0 atm. What is the volume of the gas?

Problem #3: 690.0 mL of oxygen are collected over water at 26.0 °C and a total pressure of 725.0 mm of mercury. What is the volume of dry oxygen at 52.0 °C and 800.0 mm pressure?

Problem #4: What is the volume of gas at 2.00 atm and 200.0 K if its original volume was 300.0 L at 0.250 atm and 400.0 K.

Problem #5: At conditions of 785.0 torr of pressure and 15.0 °C temperature, a gas occupies a volume of 45.5 mL. What will be the volume of the same gas at 745.0 torr and 30.0 °C?

Problem #6: What is the final volume of a 400.0 mL gas sample that is subjected to a temperature change from 22.0 °C to 30.0 °C and a pressure change from standard pressure to 360.0 mmHg?

Problem #7: 400.0 mL of hydrogen are collected over water at 18.0 °C and a total pressure of 740.0 mm of mercury.

Problem #8: The pressure of a gas is reduced to 75% of its initial value and the volume is increased by 40% of its initial value. Find the final temperature, given that the initial temperature was −10 °C.

Problem #9: The pressure of 8.06 L of an ideal gas in a flexible container is decreased to one-third of its original pressure, and its absolute temperature is decreased by one-half. What is the final volume of the gas?

Problem #10: A balloon of air now occupies 10.0 L at 25.0 °C and 1.00 atm. What temperature was it initially, if it occupied 9.40 L and was in a freezer with a pressure of 0.939 atm?

Problem #11: A gas occupies an 8.00 mL flexible-walled container. The pressure is doubled, the absolute temperature is quadrupled, and 15% of the gas leaks out. What is the new volume?

Problem #12: What is the density, in g/L, for a gaseous compound at STP if the gas in a 1.00 L bulb weighs 0.672 g at 25.0 °C and 733.4 mm Hg?

Problem #13: Predict how the volume of a given mass of gas will differ when the following changes in the temperature and pressure are made:

(a) The pressure is tripled while the absolute temperature is doubled.
(b) The absolute temperature is doubled while the pressure is reduced by half.
(c) The pressure and the absolute temperature are both doubled.
(d) The temperature is increased by four times while at the same time the pressure is doubled.

Problem #14: What is molar volume at SATP?

Problem #15: A sample of neon has a volume of 0.730 dm3 at a temperature of 21.0 °C. and pressure of 102.5 kPa. If the density of neon is 0.900 g/dm3 at 0 °C and 101.3 kPa, what is the mass of the sample?

Problem #16: Suppose the pressure on a 10.0 m3 sample gas at 12.0 °C is cut in half.

(a) Is it possible to change the temperature of the gas at the same time such that the volume of the gas doesn't change?
(b) If yes, calculate the new temperature of the gas